TIO2 Nanorods-Supported Gold Nanoparticles as Photocatalysts foe the CO Preferential Oxidation

Titanium dioxide is a robust, nontoxic and inexpensive semiconductor that presents unique and remarkable photocatalytic properties. A wide range of semiconductors have been evaluated, but a general consensus of the current literature is that only TiO2 satisfies the key criteria demanded for a good photocatalyst, even though it possesses activity only under UV light excitation, owing to the quite wide band gap, and a rapid electron-hole pair recombination. The above mentioned limitations of TiO2 can be overcome to some extent by depositing on its surface noble metal nanoparticles, such as gold, and exploiting their localized surface plasmon resonance (LSPR). It is generally agreed that the catalytic activity of Au based catalysts depends on the size of the gold particles, but also the morphology/shape of nano-scale titania supports can exhibit significant effects on the performance of noble metal based catalysts [1]. Due to their unique photophysical and chemical properties, one-dimensional TiO2 nanorods seem to play a cooperative effect with Au-NPs. This type of catalysts can be photoactive in the preferential oxidation of CO to CO2 in excess of H2 (CO-PROX). This reaction, usually carried out in the temperature range 40-200°C, is one of the most economical and efficient approaches to reduce the CO content of the on-board H2-rich gas streams produced by reforming of alcohols or hydrocarbons down to ppm level, before entering the proton exchange membrane fuel cell (PEMFC) for automative applications. In the present work we report on the photo-response behaviour of a series of Au-NPs/TiO2 nanorods systems in the CO-PROX reaction under solar-spectrum irradiation at r.t. and atmospheric pressure. Au nanoparticles (1.0 wt% nominal loading) were precipitated-deposited on TiO2 nanorods, previously synthesized by different procedures to obtain rutile/anatase pure phases and thermally treated at different temperatures to obtain mixed polymorph compositions. The impact of the Au loading and the calcination temperatures of the nanorods on the structural, physico-chemical and photocatalytic properties of Au-TiO2 catalysts were investigated by means of ICP-OES, N2 physisorption, XRD, HRTEM, DRIFT UV-visible and XPS. Catalytic tests showed differences in activity and stability among the prepared catalysts. Au/TiO2 nanorods appeared active, stable and selective in the photo-PROX, making this class of materials, coupled with solar-spectrum irradiation, a novel feasible approach to remove the trace amount of CO in H2-rich stream at low temperature